The invention relates to low melt flow compositions.
Insulating glass units often include two panels of glass separated by a spacer. The panels of glass are placed parallel to each other and the spacer is sealed to the glass. Insulating glass units also have other structures including two spacers and three glass panels. There are also a variety of spacers available including hollow metal tubes, nonmetal tubes, preformed roll type spacers, plastic spacers, metal U-channels, and various organic and inorganic foams.
Insulating glass units are prone to the accumulation of chemical xe2x80x9cfogxe2x80x9d on the interior surface of the glass panels. Fogging can be caused by off gassing of organic and inorganic materials in the spacer or from other structures in the interior of the insulating glass assembly, e.g., painted decorative grids. The spacers frequently contain a desiccant to adsorb residual moisture that may enter the airspace during the life of the unit. Desiccants are available in a variety of forms including compositions that include organic or inorganic carriers and an adsorbent capable of adsorbing moisture or volatile organic compounds. When placed in an insulating glass assembly these compositions reduce fogging.
In one aspect, the invention features a composition that includes a polyalphaolefin polymer, and from about 20% by weight to about 70% by weight adsorbent, the composition being essentially free of a film forming agent. In one embodiment, the polyalphaolefin polymer includes monomers selected from the group consisting of ethylene, propylene, butene, pentene, hexene, octene, decene, terpene, isoprene, styrene, butadiene, vinyl acetate and combinations thereof.
In other embodiments, the composition includes from about 40% by weight to about 70% by weight adsorbent. In one embodiment, the adsorbent includes an organic adsorbent. In some embodiments, the composition further includes no greater than about 10% by weight organic adsorbent.
In another embodiment, the composition, when applied to a substrate and subjected to 88xc2x0 C. for one month, is free of visible sag.
In some embodiments, the composition exhibits a melt flow time of no greater than 60 seconds, preferably no greater than 15 seconds, more preferably less than 5 seconds.
In another aspect, the invention features an insulating glass assembly that includes a first glass substrate, a second glass substrate, a separator disposed between the first glass substrate and the second glass substrate, and an above-described composition in contact with the separator.
In other aspects, the invention features a composition that includes a polyalphaolefin polymer and from about 20% by weight to about 70% by weight adsorbent, the composition exhibiting a melt flow time of less than 5 seconds at 190xc2x0 C.
In some aspects, the invention features a composition that consists essentially of a polyalphaolefin polymer, from about 20% by weight to about 70% by weight of an adsorbent selected from the group consisting of moisture adsorbents, volatile organic adsorbents, and combinations thereof, from 0 to 10% by weight tackifying resin, and from 0 to 5% by weight antioxidant. In one embodiment, the composition consists essentially of polyalphaolefin polymer and adsorbent.
A film forming agent is a material other than a polyalphaolefin polymer that forms a film or assists in forming a film including, e.g., polyisobutylene and butyl rubber.
The adsorbent composition adheres to separators (e.g., metal or plastic channels) used in insulating glass units without sagging or loss of adhesion during the useful life of the unit in which the composition is incorporated. The adsorbent composition can adsorb moisture and volatile organic compounds from its surrounding atmosphere.
The adsorbent composition is also pumpable (i.e., has a melt flow time of no greater than about 60 seconds when tested per ASTM D-1238, Procedure B using an 1100 gram load and a 6-8 gram sample, at 190xc2x0 C. (374xc2x0 F.)) and exhibits a sufficiently low melt flow time such that the composition flows easily. The adsorbent composition is particularly well suited for use in insulating glass assemblies and in processes for preparing insulating glass assemblies. Insulating glass assemblies that include the adsorbent composition can be free from fogging during the useful life of the glass assembly.
The adsorbent compositions include large amounts of adsorbent, yet exhibit melt flow times of less than 5 seconds at 190xc2x0 C.
Additional features and advantages of the invention will be apparent from the description of the preferred embodiment thereof and from the claims.